Merkle Proof Verification (Python)

import hashlib

def keccak256(data: bytes) -> bytes:
    from eth_hash.auto import keccak
    return keccak(data)

class MerkleTree:
    def __init__(self, leaves: list[bytes]):
        self.leaves = [keccak256(l) for l in leaves]
        self.layers = [self.leaves]
        self._build()

    def _build(self):
        layer = self.leaves[:]
        while len(layer) > 1:
            if len(layer) % 2 == 1:
                layer.append(layer[-1])
            next_layer = []
            for i in range(0, len(layer), 2):
                combined = keccak256(layer[i] + layer[i+1])
                next_layer.append(combined)
            self.layers.append(next_layer)
            layer = next_layer

    @property
    def root(self) -> bytes:
        return self.layers[-1][0]

    def get_proof(self, index: int) -> list[bytes]:
        proof = []
        for layer in self.layers[:-1]:
            sibling_index = index ^ 1
            proof.append(layer[sibling_index])
            index //= 2
        return proof

    @staticmethod
    def verify(leaf: bytes, proof: list[bytes], root: bytes) -> bool:
        computed = leaf
        for sibling in proof:
            computed = keccak256(computed + sibling)
        return computed == root

# Usage
addresses = [b"0x1234...", b"0x5678...", b"0xabcd..."]
tree = MerkleTree(addresses)
proof = tree.get_proof(0)
print("Valid:", MerkleTree.verify(tree.leaves[0], proof, tree.root))